Pauling's idea for a plasma substitute was not an unfamiliar one. Gelatin was already in use as a plasma replica during the late 1930s and early 1940s, but its viscosity and tendency to condense at room temperature made it a poor candidate. The U.S. military needed something quick and efficient that could be used in field hospitals with minimal preparation. The Caltech team, however, was not yet ready to discard gelatin as a potential candidate. Pauling hoped that, through chemical processes, he might be able to transform standard commercial-grade gelatin into a workable substance.

Between June 1942 and May 1944, Caltech received approximately $20,000 from the CMR in support of the project. During that time, Pauling and his team were able to successfully develop a possible plasma substitute through the polymerization and oxidation of gelatin. This substance, first referred to as polyoxy gelatin and eventually known as Oxypolygelatin, was superior to its unmodified counterpart in several ways. Because it was liquid at room temperature, Oxypolygelatin did not require the same pre-injection heating that previous substitutes required, allowing it to be used quickly and without the help of heating implements. Furthermore, thanks to the creation of large chain-like molecules during the preparation process, oxypolygelatin was retained in the bloodstream for longer periods, allowing the patient's body more time to manufacture natural plasma. Finally, where gelatin contained pyrogens (fever-causing molecules), Oxypolygelatin did not - a property resulting from the addition of hydrogen peroxide.

To a chemist's eye, Oxypolygelatin appeared to be an acceptable substitute for human plasma. Pauling knew, however, that his own tests were not enough to convince the CMR of the substance's viability. He needed a medical expert's stamp of approval. Pauling called on Dr. Thomas Addis - the renal expert who cured Pauling's near-fatal case of glomerular nephritis - to analyze the effects of Oxypolygelatin on human organs. Addis accepted the challenge, bringing fellow researcher Dr. Jean Oliver to the project as well. Over the next two years, Addis and Oliver subjected Oxypolygelatin to a battery of tests, eventually confirming its potential as a plasma substitute.

Despite Pauling's enthusiasm and Addis' promising results, the CMR did not believe Oxypolygelatin to be sufficiently superior to the pre-existing gelatin substance and, in the spring of 1944, the committee refused Pauling's request for a renewal of contract. Surprised by the committee's decision, he submitted a second request, asking that his contract be renewed for the period of four months, with no additional funding from the OSRD. His request was granted but, due to empty coffers, no progress was made. Pauling applied again in June, this time requesting extra resources for the project. Again, he was denied.

Frustrated with the lack of support, Pauling and his team scraped together enough residual funds to allow for one more series of experiments. Pauling began injecting mice and rabbits with his synthetic plasma, carefully monitoring their health and examining blood samples to determine the effects of the treatment. The results were satisfactory but not enough to put the project back in the good graces of the CMR. Pauling knew that the only way to stimulate interest (and funding) for the project was to prove that his substance could be used in humans. In September of 1944, twelve patients at the Los Angeles General Hospital were injected with Oxypolygelatin, all exhibiting favorable reactions. Pauling had the results he needed.